Sodium and water accumulation in an injured cell are a direct result of:

Choice A: Move Na Inside the Cell

The primary function of the Na-K pump, also known as the sodium-potassium pump, is to move sodium (Na) ions out of the cell, not into the cell. This pump actively transports three sodium ions out of the cell for every two potassium ions it brings in. Therefore, this choice is incorrect.

Choice B: Move K Out of the Cell

The Na-K pump moves potassium (K) ions into the cell, not out of the cell. This active transport mechanism helps maintain the necessary concentration gradients of sodium and potassium across the cell membrane, which are crucial for various cellular functions, including maintaining the resting membrane potential.

Choice C: Move Na Out of the Cell

The main function of the Na-K pump is to move sodium ions out of the cell. For every cycle of the pump, three sodium ions are exported out of the cell, and two potassium ions are imported into the cell. This process is essential for maintaining the electrochemical gradient across the cell membrane, which is vital for nerve impulse transmission, muscle contraction, and overall cellular homeostasis.

Choice D: Move Na and K Inside the Cell

This choice is incorrect because the Na-K pump does not move both sodium and potassium ions inside the cell. Instead, it moves sodium ions out of the cell and potassium ions into the cell. This active transport mechanism is crucial for maintaining the proper ionic balance and membrane potential necessary for various physiological processes.

Choice A: Hypoventilation

Hypoventilation refers to inadequate ventilation that leads to an increased concentration of carbon dioxide (CO2) in the blood, resulting in respiratory acidosis. This condition is characterized by a decrease in blood pH due to the accumulation of CO2, which forms carbonic acid. Hypoventilation does not cause metabolic acidosis, as it primarily affects the respiratory component of acid-base balance.

Choice B: Massive Blood Transfusion

Massive blood transfusion can lead to metabolic alkalosis rather than metabolic acidosis. This is because stored blood products often contain citrate, which is metabolized to bicarbonate in the liver, increasing the blood’s alkalinity. Additionally, the transfusion of large volumes of blood can dilute the plasma bicarbonate concentration, but this typically does not result in metabolic acidosis.

Choice C: Kidney Failure

Kidney failure is a common cause of metabolic acidosis. The kidneys play a crucial role in maintaining acid-base balance by excreting hydrogen ions (H+) and reabsorbing bicarbonate (HCO3-). When the kidneys fail, they are unable to remove sufficient acids from the blood, leading to an accumulation of metabolic acids and a decrease in blood pH. This condition is known as metabolic acidosis and can result from chronic kidney disease (CKD) or acute kidney injury (AKI).

Choice D: Hyperventilation

Hyperventilation leads to respiratory alkalosis, not metabolic acidosis. This condition occurs when there is excessive ventilation, causing a decrease in CO2 levels in the blood and an increase in blood pH. Hyperventilation reduces the concentration of carbonic acid, leading to an alkaline state. It does not contribute to metabolic acidosis, which involves an imbalance in the metabolic components of acid-base regulation.